File access within a computer system is realized through a combination of three programs: application; file system (middleware); and device driver. Here, application refers to various application programs such as word processors and CAD software. Device driver refers to a control program which performs read/write on each area within a (nonvolatile) secondary memory, such as magnetic disks and flash memory, wherein stored contents are retained even when power is tuned off. File system (middleware), which is provided between application and device driver, performs a process for outputting instructions corresponding to the write instructions from the application to the device driver.
With a file system such as this, when power supplies were unexpectedly cut off during writing data and a write failure occurs, problems frequently lie in how the information in the file relevant to the write is restored. From this relation, methods addressing write failures such as this are disclosed in many references such as Patent Reference 1.    [Patent Reference 1]    Japanese Patent Laid-Open Publication No. 2003-169293 “Data recorder/player, means for recording and playing data, and digital camera”